1. Field of the Invention
The present invention relates generally to the monitoring and/or control of chemical and petrochemical production and, more specifically, to the use of Raman spectrometry in the monitoring and/or control of polyolefin production.
2. Description of the Related Art
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
As chemical and petrochemical technologies have advanced, the products of these technologies have become increasingly prevalent in society. In particular, as techniques for bonding simple molecular building blocks into longer chains, or polymers, have advanced, the polymer products, typically in the form of various plastics, have been increasingly incorporated into various everyday items. For example, polyolefin polymers, such as polyethylene and polypropylene and their copolymers, are used for retail and pharmaceutical packaging, food and beverage packaging (such as juice and soda bottles), household containers (such as pails and boxes), household items (such as appliances, furniture, carpeting, and toys), automobile components, pipes, conduits, and various industrial products.
Specific types of polyolefins, such as high density polyethylene (HDPE), have particular applications in the manufacture of blow-molded and injection-molded goods, such as food and beverage containers, film, and plastic pipe. Other types of polyolefins, such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), isotactic polypropylene (iPP), and syndiotactic polypropylene (sPP) are also suited for similar applications. The mechanical requirements of the application, such as tensile strength and density, and/or the chemical requirements, such thermal stability, molecular weight, and chemical reactivity, typically determine what polyolefin or type of polyolefin is suitable.
One benefit of polyolefin construction, as may be deduced from the list of uses above, is that it is generally non-reactive with goods or products with which it is in contact. This allows polyolefin products to be used in residential, commercial, and industrial contexts, including food and beverage storage and transportation, consumer electronics, agriculture, shipping, and vehicular construction. The wide variety of residential, commercial and industrial uses for polyolefins has translated into a substantial demand for raw polyolefin which can be extruded, injected, blown or otherwise formed into a final consumable product or component.
To satisfy this demand, various processes exist by which olefins may be polymerized to form polyolefins. Typically, these processes are performed at petrochemical facilities, which have ready access to the short-chain olefin molecules such as ethylene, propylene, butene, pentene, hexene, octene, and other building blocks of the much longer polyolefin polymers. Regardless of which process is used, the polyolefin product may deviate from the desired product in various ways. For example, the polyolefin product may have a different mechanical properties, such as density, hardness, or flexibility, and/or chemical properties, such as melting temperature or melt flow index, than what is desired. These deviations may arise for various reasons, such as varying catalyst activity, reactant purity, improper reaction conditions, transitions between product grades, and so on. However, if the deviation is not discovered until late in the reaction process, significant resources, both in material and energy, may be spent producing an unacceptable polyolefin product.
Similarly, after the polyolefin product is produced, further downstream processing, such as extrusion and additive addition, may occur. These downstream processes offer further opportunity for deviation from the desired final product and may also result in wasted resources if the deviations are not discovered in a timely manner. Therefore, both in the production and in the processing of the polyolefin product, it is desirable to discover deviations as rapidly as possible and, where appropriate, to make corrections to the processes to minimize the waste of product or resources.